Volt & Amp gauges

[Ex- Member]

When I fitted a new battery bank last year I also made a small panel with a volt and am meter and fitted into the boats engine panel. For some reason though I wasn't getting correct readings and basically gave up on them. Decided though to take another look this morning.

 

 

The volt meter requires an independent 12v supply so I have a wee 12v battery I charged up last week for that.

 

the amp meter the last time I tried wouldn't 0.00

 

Anyway today I checked through everything again. I then realised there's an adjusting screw in the back of the Volts unit. Also The sensor wires to the battery terminal were pretty thin so thought I might change it. I then realised that the Sterling battery charger is right next to the amp & volt meter. As we cc there's little chance of getting mains leccy to charge the BB, so I removed the 2 heavier cables from the charger and made a small wood terminal block with 2 x 5mm posts.

 

 

The wires from the volt meter then go to those terminals for the volts reading. I have 2 multi testers so took readings and got the volt meter reading spot on.

 

We've been relying on a gauge but it just isn't the same so hopefully we can monitor more efficiently.

 

We also sorted the amps and zeroed it in. with everything disconnected. We then switched various appliances on. We're quite surprised how little the inverter uses on standby, just 0.3 amps. We thought this was too low and thought something was wrong. However on switching on other equipment together and individually it was all adding up ok and very accurately, so we can only assume it's right.

 

What's even more surprising is that with just the fridge and inverter running total draw reads 1 amp and that's with the fridge on coldest setting.

 

Maybe this is why we have so much power, there was no sun at all all day yesterday, we've used energy as usual and batteries haven't gone below half. Bit of sun this morning but mainly overcast but bright, batteries nearing full already.

 

Is the solar energy entering the battery bank having an effect on the amps reading though.

 

Comments welcome please.

Edited September 12, 2013 by Julynian

[Mike Tee]

You changed a couple of words while I was responding!

[Ex- Member]

You changed a couple of words while I was responding!

 

Apologies LOL

[MikeV]

What's even more surprising is that with just the fridge and inverter running total draw reads 1 amp and that's with the fridge on coldest setting.

Where is the shunt? Are you measuring current in and out through the shunt, or just load current?

 

I have two ammeters. One is on the main wire from the batteries so measures net current into/out of the batteries including solar/alternator/charger current. The other ammeter is after all the charging feeds so just measures load current. My 12V Shoreline fridge draws 3.2amps so a mains fridge via an inverter is going to be at least that.

[Ex- Member]

Where is the shunt? Are you measuring current in and out through the shunt, or just load current?

 

I have two ammeters. One is on the main wire from the batteries so measures net current into/out of the batteries including solar/alternator/charger current. The other ammeter is after all the charging feeds so just measures load current. My 12V Shoreline fridge draws 3.2amps so a mains fridge via an inverter is going to be at least that.

 

Hi Mike

 

Maybe this is the problem.

 

The only shunt fitted is below in the photo In the Black fronted enclosure on left of bank.

 

 

The only thing connected on the battery side of the shunt is battery leads, and the shunt sensor wire in it's correct position.

 

Batteries are receiving constant charge from 500w solar panels.

 

Although fridge is 240v it's A+ rated and 117KWH Per Year, so a pretty efficient fridge.

[MikeV]

So from the picture of the shunt it looks like the current you are measuring is the net current - amps out minus amps in. Fridge compressors are controlled via a thermostat and mains fridges, when running, typically consume about 65 watts. Fed from an inverter that would be about 5.5 - 7.0 amps at 12 volts, depending on the efficiency of the inverter. Of course the fridge will not be running all the time and the more efficient it is, the less it should run. It will consume near zero power when the compressor is not actually running.

 

If you are seeing the 1 amp out of the batteries when the compressor is running, and assuming there are no other devices consuming power, it would suggest that the solar panels are delivering 4.5 - 6.0 amps of the current required by the inverter/fridge and therefore the 1 amp on the meter is just the net drain on the batteries.

 

What's the device on the extreme right? It look like a fuse with a switch on it - going to nowhere!

[Captain Fizz]

What a nice neat wiring setup..........lush!

[Ex- Member]

So from the picture of the shunt it looks like the current you are measuring is the net current - amps out minus amps in. Fridge compressors are controlled via a thermostat and mains fridges, when running, typically consume about 65 watts. Fed from an inverter that would be about 5.5 - 7.0 amps at 12 volts, depending on the efficiency of the inverter. Of course the fridge will not be running all the time and the more efficient it is, the less it should run. It will consume near zero power when the compressor is not actually running.

 

If you are seeing the 1 amp out of the batteries when the compressor is running, and assuming there are no other devices consuming power, it would suggest that the solar panels are delivering 4.5 - 6.0 amps of the current required by the inverter/fridge and therefore the 1 amp on the meter is just the net drain on the batteries.

 

What's the device on the extreme right? It look like a fuse with a switch on it - going to nowhere!

 

Hi Mike

 

The switch/fuse/breaker is where the solar comes in now, solar wasn't fitted or running when that photo was taken.

 

I did wonder about amps coming in. Thing is we tested other stuff by switching everything off and selecting items one at a time to switch on and note the draw.

 

So 4 led lights drew 0.6 amps

Toilet fan 0.3 amps

Desk fan 2.5 amps

6 inch comp fan 0.3 amps

Tv booster 0.2 amps

All 12v

 

All the amperages recorded matched the stated amps on the equipment almost exactly.

 

We also did the same later with solar disconnected, and the equipment all draws the same and the fridge draws the same as before.

 

We're having one of our lowest energy days today, currently @ 12.63 volts, I think that's ball park 50% SOC

 

ETA 12v TV 3.6 amps

Edited September 12, 2013 by Julynian

[MikeV]

Was the compressor on the fridge actually running when you measured the 1 amp? I would expect an efficient fridge to be only running for about 25-35% of the time provided it is well ventilated at the back. You should be able to hear a slight hum from the fridge when the compressor is actually running.

 

Our Shoreline is very quiet. You only hear at night when there is no other background noises.

[Ex- Member]

Was the compressor on the fridge actually running when you measured the 1 amp? I would expect an efficient fridge to be only running for about 25-35% of the time provided it is well ventilated at the back. You should be able to hear a slight hum from the fridge when the compressor is actually running.

 

Our Shoreline is very quiet. You only hear at night when there is no other background noises.

 

It was running, had to wait about 15 minutes with the door open though LLOL when it kicked in the 0.3 jumped to 1amp we hung on for about 5 minutes and it just staid at that. It is well ventilated and I have floor fans, but of course not running when we tried this. but there are holes in the floor just below the fridges motor, so cool air is readily available.

 

It's possible I suppose the fridge regenerates in stages and uses more amps as it continues to run.

 

I think I'll do some more investigating, I know our fridge is very energy efficient. But running at 0.7 amps is way better than the 117kwh per year quoted.

 

It's a very quiet fridge as well but if next to it in the middle of the night you do hear it clicking on, although rarely. We do keep the fridge pretty full with food and drinks as well.

 

It niggles me when things don't make sense LOL

[Ex- Member]

What a nice neat wiring setup..........lush!

 

Thanks captain.

 

I had some really good advice from some forum members. nicknorman and smileypete to name just 2 so made sure I did a good job.

 

 

I even made my own battery connection posts using 12mm Brass studding, cables connect above and below the floor. found some nice battery boxes and used up some off cut oak.

 

The full thread is here

 

http://www.canalworld.net/forums/index.php?showtopic=46977

 

called battery cabling, quite handy as I basically had step by step instructions which will probably be useful info for others.

Edited September 12, 2013 by Julynian

[Captain Fizz]

Quality, tidy wiring was one of the things that helped our choice when we bought Cariad!